1. Field of the Invention
The present invention relates to lightweight concrete panel with a supporting steel frame and the device that connects the concrete facing to the steel frame.
2. Description of the Related Art
The following patents define the current state of the art:
Schilger, U.S. Pat. No. 4,602,467 describes a building panel with a supporting steel frame attached to a concrete slab. The attaching mechanism that connects the steel frame to the concrete slab is part of the stud members. The flange of one side of the stud member is punched and modified in various shapes intending to act as anchor when its entire side is embedded into the concrete slab. Because of the stud's flange embedment into the concrete, the panel is considered a composite panel where both the concrete layer and the steel frame plays important role on carrying load.
Schilger, U.S. Pat. No. 4,885,884 describes a building panel with a supporting steel frame attached to a concrete slab. The attaching mechanism that connects the steel frame to the concrete slab is part of the stud members. The attaching device of this panel is not one long section extending one whole side of the stud member like his earlier art U.S. Pat. No. 4,602,467. Instead, the multiple connecting devices are the intermittingly punched and bent portions in the C-section stud's flange. The punched and bent sections can be L-shaped, V-shaped, and T-shaped sections that run parallel to the stud member and extend into the concrete slab, acting as the connecting devices.
Ruiz, U.S. Pat. No. 6,151,858 has a similar concept as Schilger in U.S. Pat. No. 4,885,884. Ruiz's intermittingly punched and bent sections in the stud's flange have a different shape and bent direction. Ruiz's protruding L-shaped is narrower than Schilger and bent differently. Like Schilger's protruding sections, Ruiz's punched tabs are the connecting devices that are part of the stud member.
Bodnar, U.S. Pat. No. 4,909,007 has a similar concept as Schilger, U.S. Pat. No. 4,602,467. One entire side of the C-section stud is punched and bent into one L-shaped flange, forming one long integrated attaching device to be embedded into a concrete slab. The differences in Bodnar's art are the openings in the embedded L-shaped junction flange and the large opening in the stud web area. The openings in the embedded junction flange are claimed to enable material to flow through and form a stronger concrete in the local region. The large openings in the stud web are meant to limit the thermal conductivity from one side to the other through reducing the thermal pathway or steel area in the stud web.
There are three major problems that associate with all mentioned arts: first is that they will need specially designed machinery to create such special stud with integrated connecting mean; second is their poor thermal performance; and third is the meeting of the building code specifications. Generally, the cost of specially engineered machinery to produce such modified stud is expensive and prohibiting. The thermal performance of Ruiz's and Schilger's wall panels is poor due to the direct material contact between the stud flange and the exterior concrete slab. Metal has high temperature conductivity and the heat from the exterior concrete flows right though the metal material of the stud to the inside stud flange. Although Bodnar's opened web stud is an improvement in reducing thermal conductivity in the stud web, the cost of machinery that produces the openings in stud web is expensive and prohibiting due to its complex process. Bodnar's opened web stud is an improvement, but the bottom and top tracks in his steel frame still have solid web so the panel still has poor thermal performance in those areas of the panel. In load-bearing applications, Bodnar and Schilger's wall panel will not meet the current International Building Code specifications in many parts of the country and the world. Little is known about the composite action between the concrete slab and the steel frame in their design. There is no guidance in the code specifications to cover such panel constructions. Assuming any unique composite panel is tested and proven to have structural properties, the submitting of its data and getting it specified in the code specifications can be a very long and costly process. The wide adoption of any unique composite panel is very unlikely because code specifications are written to encompass a type of construction not of any specific product. Previous arts overlooked these three major issues. The present invention was developed to overcome these major problems inherent in all prior arts.